Another recommendation for SAN. The USS Midway was an excellent day, one of the best.

If you want to drive a bit then you could take in Phoenix (Scottsdale is a bit nicer and some decent resort hotels there, though quite warm in August!) then maybe the Grand Canyon, then back to LA.

Actually, scrub that, might be too much driving for your kids, just seen their ages.

Still, lots to do in the part of the world, you won't get bored.